The present invention relates to the field of apparatus and methods for moving cartridges between automated data cartridge libraries.
Automated data cartridge library systems are available in many shapes and sizes. The most common library systems are configured as either a two-dimensional array of storage cells that resemble bookshelves, or a cylinder of storage cells that resemble farm silos. The cylindrical, or silo type of library is popular because the robotic arm within the silo is never more than one half the silo away from the next desired cartridge, the enclosed shape acts as a shield between the human operator and the robotic arm, and several silos can be arranged in a honeycomb pattern allowing the library system to grow incrementally.
A load/unload port is usually provided in the side of the silo for inserting new cartridges into a silo and removing existing cartridges. Large library systems often have a few, or even just one load/unload port for the entire system for economical reasons. For this, and others reasons, pass through ports are installed between adjacent silos in a multi-silo library system to allow for the transfer of cartridges between adjacent silos. Moving a cartridge starts when the robotic arm of the sending silo acquires the cartridge and places it in the pass through port. The robotic arm in the adjacent silo then moves the cartridge from one pass through port to another pass through port. This process is repeated by each robotic arm in each silo along the cartridge""s route until the cartridge reaches the receiving silo. Moving the cartridge through several silos is time consuming and disrupts the operations of the silos along the route. Each silo along the cartridge""s route must spend some time moving the cartridge from one pass through port to another. In practice, error recovery routines cause all of the robotic arms and pass through ports along the cartridge""s route to halt all other operations until the routing is complete. A considerable portion of a library system can be brought to a halt during long cartridge moves. When many inter-silo cartridge moves are required, the overall library system performance decreases.
Pass through ports place constraints on the layout of multi-silo library systems. Silos must be placed adjacent to at least two other silos to allow the cartridges to pass through. The adjacent requirement means that all of the silos must reside in the same room. Support columns and partial walls within the room further constrain silo placement. Maintenance and other human access requirements also constrain silo layout to no more than two rows wide.
Several patents have been issued disclosing mechanisms for moving cartridges between adjacent and neighboring storage units within a library system. U.S. Pat. No. 5,388,946 issued to Baur on Feb. 14, 1995, discloses a robot that moves on rails across the face of a two-dimensional storage array. The main task of the robot is to move cartridges between the storage array and read/write drives and between different slots in the same storage array. While the robot is moving the cartridge between storage arrays and read-write drives, no other cartridges can be accessed and moved to other locations.
U.S. Pat. No. 5,703,843 issued to Katsuyam et al. on Dec. 20, 1997, discloses a rail-based robotic accessor that moves cartridges between multiple storage drum units and read/write drives. While this robotic accessor is manipulating a cartridge in one storage drum unit, no other cartridges in that drum unit can be accessed and transported to other locations.
U.S. Pat. No. 5,570,337 issued to Dang on Oct. 29, 1996, discloses a rail-based media carriage that moves cartridges between adjacent columns in a multi-column library system. This design allows a media transport apparatus associated with each column to move other cartridges between the read/write drives and storage slots of the column while the media carriage is moving a cartridge between columns. A limitation of this design is that the media transport apparatus and media carriage must meet at predetermined positions at the same time so that the media transport apparatus can insert and remove a cartridge from the media carriage. While the media carriage is waiting at one of the predetermined positions no other cartridges can be moved between columns.
U.S. Pat. No. 5,429,470 issued to Nicol et al. on Jul. 4, 1995, discloses a transport conveyer belt mechanism that moves cartridges between adjacent columns in a multi-column library system. Each column has its own belt. To the left and right of each belt, except the two end belts, are the belts of the adjacent columns. A cartridge placed on one belt is moved from belt to belt, from column to column until the cartridge reaches the receiving column. Similar to the media carriage in the Dang patent, the belt of the receiving column must hold the cartridge at a predetermined position until the gripper mechanism of the receiving column removes the cartridge from the belt. While this belt is waiting, it blocks other cartridges that must be routed through that column.
U.S. Pat. No. 5,395,199 issued to Day, III et al. on Mar. 7, 1995 discloses a robotic car-based system for use with a horizontal storage array. The storage cells for this library system create a floor across which one or more robotic cars operate. Each robotic car can move anywhere across the floor. The robotic cars move the cartridges between storage cells and the read/write drives. They may also be used to move cartridges from one horizontal storage array to another. One limitation of this design is that each storage array must be oriented horizontally, or near horizontal thus they consume a large amount of floor space. Another limitation is that the robotic cars must carry their own power source to allow free movement on the floor. This means that the robotic cars must be taken out of service occasionally for recharging. Finally, the robotic cars must carry optical sensors and processing circuitry of sufficient complexity to provide an ability to sense and follow optical patterns positioned on the floor.
What is desired is a rail-like transport system that operates external to the individual libraries to move the cartridges between the libraries. This approach makes moving cartridges long distances efficient since only the sending and receiving libraries are involved with the move. The system should include at least one port at each library to allow asynchronous operation between the robotic arms inside each library and the carriages moving between libraries along the rails. Rail-like systems also make the configuration of the overall library system more flexible since the libraries do not have to be adjacent, in the same room, or even on the same floor in the building. Finally, the use of rails or other guiding structures simplifies the propulsion and guidance requirements imposed on the carriages.
The present invention is a system and a method for moving cartridges between individual cartridge libraries of a multi-library system. The system includes one or more transport robots operating on one or more guide structures. The transport robots carry the cartridges independently of all individual libraries, except the sending and receiving libraries. This frees the libraries between the sending library and the receiving library from involvement in the cartridge moves.
Simple transport robots carry one cartridge at a time. Movement of multiple cartridges requires one transport robot to make several trips, or several transport robots to operate together. Complex transport robots may carry up to several cartridges simultaneously.
One or more load ports at each library transfer the cartridges between the transport robots and the robotic arm inside the library. The load ports can hold the cartridges to allow for asynchronous operations between the transport robots and sending/receiving libraries. Simple load port may handle only one cartridge at a time. Complex load port may handle several cartridges simultaneously.
The guide structures may be routed through one, two or all three dimensions. The flexibility of the guide structure routing allows individual library placements to account for walls, columns, floors, ceilings, and other physical obstacles. It is not necessary that individual libraries shall be adjoining. The guide structures may take on one of several forms including rails, tubes, channels and cables. Junctions such as switches, turntables, elevators and the like couple multiple guide structures.
One or more controllers coordinate transport robot and cartridge movement. One controller may be used to coordinate the entire multi-library system, or distributed controllers may be used to divide the workload. Local controllers may be mounted on each transport robot to provide greater capability or even autonomy.
Communications between the various libraries, load ports, transport robots and controllers may be accomplished through hard wires or wireless links. Wireless communications links may be in the form of radio links, optical links, acoustic links or other technologies. Wired communication links may be in the form of electrical or fiber optic cables tethered to the transport robots, or electrical signals passed through the guide structure itself.
Power for moving the transport robots may be incorporated into, or external to the transport robots. External propulsion methods include air pressure, cables and belts. Onboard propulsion methods include electric motors powered from onboard batteries, or from electrical power received through the guide structure.
Either the transport robot, the load ports, or both have grippers to exchange the cartridges between the transport robots and load ports. Load port to library exchanges may be handled solely by the library""s robotic arm, or with the assistance of load port. Transfer of cartridges between transport robots may be performed directly by the transport robots, or with the aid of a transfer mechanism situated at strategic positions along the guide structures.
Accordingly, it is an object of the present invention to provide a system and a method for moving cartridges between libraries of a multi-library system where only the sending and receiving libraries are involved with the move.
Another object of the present invention is to provide for asynchronous operations between the robotic arms inside the libraries and the transport robots that move the cartridges between the libraries.
Yet another object of the present invention is to allow multi-library layouts to account for walls, columns, floors, ceilings, other physical obstacles and maintenance considerations that make it difficult to place individual libraries adjacent each other.
These and other objects, features and advantages will be readily apparent upon consideration of the following detailed description in conjunction with the accompanying drawings.